Induced-current brake traction drive control



p 21, 1954 F, w. WENDELBURG 2,689,934

INDUCED-CURRENT BRAKE TRACTION DRIVE CONTROL Filed May 27, 1949 2Sheets-Sheet l 3 INVENTOR.

M ill. G14

dlt'arny P 21, 1954 F. w. WENDELBURG 2,689,934

INDUCED-CURRENT BRAKE TRACTION DRIVE CONTROL Filed May 27, 1949 2Sheets-Sheet 2 INVENTOR. fflowaua BY M q 5 m dkorney Patented Sept. 21,1954 INDUCED-CURRENT BRAKE TRACTION DRIVE CONTROL Frank W. Wendelburg,to Harnischfeger Cor Milwaukee, Wis., assignor poration, Milwaukee,Wis.,

a corporation of Wisconsin Application May 27, 1949, Serial No. 95,807

9 Claims. 1

This invention relates to electrically actuated propelling andcontrolling means for self propelled traction apparatus such astravelling overhead cranes and it resides in an improved form of suchapparatus in which novel driving andbraking means operate in such manneras to cause the travelling movement to be arrested without hazardous orundesirable mechanical shock, said result being accomplished through theuse of induced current or eddy-current torque resisting means, mountedin driven relationship to the propelling mechanism, the same beingenergized so as to become active to restrain motion, only when anoperator actuates a controller from a higher speed driving position to aposition calling for deceleration.

One object of this invention is to provide a propelling and controllingapparatus which will permit motion to be smoothly terminated withoutdependence upon manually operated brakes.

Another object of this invention is to provide propelling andcontrolling means for the bridge of an electrically driven travellingoverhead crane wherein motion is arrested smoothly by means which may becontrolled from a point located in a travelling operators cab attachedto the crane trolley.

Another object of this invention is to provide a propelling andcontrolling apparatus for the bridge of an electrically driven overheadcrane which will safely and smoothly arrest motion of the crane in theevent of power failure.

Another object of this invention is to provide a propelling andcontrolling apparatus for the bridge of an electrically driven overheadcrane which will make practical increased rates of travel of the bridgeof the crane in spite of the use of a trolley mounted operators cab,without hazard to the operator due to excessive mechanical shock duringstopping.

The foregoing and other objects and advantages of this invention areexplained in the description which follows, which description is setforth with reference to the accompanying drawings forming a part hereof,in which there is shown, for purposes of illustration and not oflimitation, one form in which the apparatus of this invention may beembodied.

In the drawing, Fig. 1 is an electrical circuit diagram of one form ofthe apparatus of this invention,

Fig. 2 is an end view in elevation diagrammatically depicting one formof crane with which the circuit set forth in Fig. 1 may be employed, and

Fig. 3 is a diagrammatic side view in elevation of the crane shown inFig. 2.

For the driving of overhead cranes and other traction devices it isdesirable at times to employ alternating current driven electricalequipment. The usual wound rotor induction motor, having control meansfor reversing the same and regulating the speed thereof, used for thispurpose is subject to certain limitations, one being the fact that sucha motor is ill adapted to perform a braking function. Consequently sucharrangements have usually depended upon friction service brakes, whichare manually applied to produce the desired gradual deceleration priorto the sudden stoppage produced by the usual electro-magneticallyreleased, normally applied, friction holding brakes which become appliedwhenever power supplied to the motor is interrupted. This arrangement,however, has been suitable only in cranes or other devices having theoperators cab so mounted as to make feasible the necessary mechanical orhydraulic connections between the operators cab and the service brakes.

In certain instances,- it is necessary that the operators cab be movablein relation to the traction device per so, as is thecase where the cabis attached to the trolley of an overhead crane, so as to movelengthwise of the bridge of the crane to permit the operator to maintaina position approximately above the load being lifted. Such cranes areparticularly useful where special grapples are employed enabling theoperator to engage and release a load without assistance of a groundcrew, as for example in the case of lumber cranes. Trolley mounted cabsare also of use in foundry cranes where pouring from a moving ladle isdesired and also to a smaller extent in cranes employing clam shells,magnets or other devices which load without the attention of a groundcrew. Heretofore in cranes having trolley mounted operators cabs,because of the difiiculty of connecting up manually actuated servicebrakes, stopping of bridge travel has usually been made to depend uponthe so-called holding brake which becomes applied upon discontinuance ofpower supplied to the propelling motor. The sudden stopping produced bythe holding brake, particularly when applied while the bridge isdrifting at a rapid rate, causes serious mechanical shocks. As a resultit has been customary to limit the rate of travel of the bridge of suchcranes to speeds which are but a minor fraction of bridge-travel speedsotherwise considered suitable. Unless this precaution is observed themechanical shocks are sufficiently severe to subject the entirestructure to conditions endangering its structural soundness and tothrow the operator about in his control cab with such violence as tomake injury likely.

Through the use of the improved apparatus of this invention it ispossible to provide alternating current driven traction devices such asoverhead cranes in which the rate of travel can be greatly increasedwithout hazardous or undesirable shocks during stopping and withoutdependence upon manually actuated service brakes.

The apparatus of this invention is suitable for use in connection with awide range of electrically driven self-propelled apparatus andparticularly in connection with cranes of the general typediagrammatically depicted in Figs. 2 and 3. The crane there shownincludes a traction device in the form of a horizontal bridge I mountedupon end trucks 2 and 3 which in turn are carried for horizontal rollingmovement upon runways 4 and 5. Mounted for horizontal transversemovement across the top of bridge I is a trolley 6 from which hoistinglines 1 and 8 extend downwardly as shown. Secured to the trolley 6,through extensions 9 of the trolley frame, is an operator's cab l8.

The propelling apparatus causing motion of the bridge I upon the runways4 and comprises, as shown more clearly in Fig. 3, a propelling motor IIto which a normally applied holding brake I2 is secured and from whichan output shaft l3 extends. Also forming a part of the propellingapparatus is a reduction gearing |4 connected in driven relationship tothe shaft l3. From the reduction gearing [4, cross shafts l5 and I6extend to and drivingly join with the trucks 2 and 3 at the ends of thebridge.

In accordance with this invention there is associated in torqueresisting relationship to the drivin train of the bridge I, aneddy-current or induced-current brake H which is mounted in the instanceshown on an extension of shaft l3. The induced-current brake I1 is ofwell known form, comprising stationary and rotating magnetic memberswith windings which may be energized to establish a magnetic fieldmutual to the two members which field gives rise to torque-resisting,induced currents when relative rotation between the two members takesplace. Since the details of induced-current or eddycurrent brakes (withand without conductor bars) are well known and form no part of thisinvention the same are not shown herein otherwise than diagrammaticallyand the term induced-current brake is used herein as descriptive of thegeneral class of such devices.

As shown more clearly in Fig. 1, the primary supply leads l8, I9 and28of motor II are joined with trolley conductors 2|, 22 and 23 mountedupon the bridge I, but not there shown. Extending from the operators cabID in sliding electri-v cal contact with conductors 2|, 22 and 23 areprimary supply connections 24, 25 and 26 which join as shown with mainreversing contactors 21 and 28. The reversing contactors 21 and 28 areconnected in turn through appropriate leads with power supply mains29,38 and 3|. Mains 29, 38 and 3| in turn receive power, from trolleyconductors 32, 33 and 34 attached to bridge I.

The admission and regulation of power supplied to motor is arranged tobe controlled by a drum or other suitable type of controller designatedgenerally by, the numeral 35'... Controller 4 35, in the particularinstance shown, is provided with an off position and five forward andfive reverse positions.

First forward position of controller Upon movement of controller 35,shown in off position in Fig. 1, to the first forward position, segments36 and 31 engage their respective stationary contacts which are joinedby leads 38, 39 and 48 with power main 3|, thus establishing acontrol-current supply connection for all of the segments of controller35. At the same time segment 4| of controller 35 makes contact with its.respective stationary contact and thus through lead 42 provides acircuit which joins with winding 43 of contactor 28. The oppositeterminal of winding 43 is joined in turn through lead 44, inter-lockingcontacts 45, and leads 46, 41 and 48 with supply main 29. Contactor 28is thus caused to close, establishing current supply to the primary ofmotor H for forward driving of the same. The secondary of motor II isjoined throughleads 49, 58 and 5| with trolley conductors 52, 53 and 54,and thence by sliding contact leads 55, 56 and 51, with a resistancegrid, generally designated by the numeral 58. Under this condition thefull resistance of the grid, 58 is included in the secondary circuit ofthe motor I and forward driving at the lowest speed of motor takesplace.

Upon closure of main contactor 28, closureof auxiliary contacts 59provides a connection from supply main 3| through lead 48, lead 68 andlead 6| with lead 62 which joins in turn with the winding of lock-inrelay 64. The other end of the winding of relay 64 is joined in turnthrough lead 65 with lead 41 and thus throughlead 48 with supply main29. The lock-in relay 64 is thus caused to close for a purpose hereafterdescribed.

Movement of the controller 35 from "off" to the first forward positionalso bring segments 66,61 and 68 into engagement with their respectivestationary contacts but theseengagemenrs are temporarily without effectfor reasons which will be more fully explained.

In order that motor ll be permitted to freely rotate with the controllerin the first forward position it is necessary that holding brake "bereleased and provision for such release is made through holding brakewindings 69 and 18. The windings 69 and 18 are joined by a commonlead 1|with one output terminal of rectifier 12 and by leads 13 and 14, whichextend through the contacts of normally open holding brake relay 15 andlead 16 to the opposite output terminal, of rectifier 12. The rectifier12- is supplied with alternating current whenever, the primary of motorH is energized through leads 11 and 18 which extend to primary leads l9and 28 of motor Leads 11 and 18 also serve to energize the winding ofholding brake relay 15. Thus whenever the primary of motor is energizedholding,

brake relay 15 is caused to close and the output of rectifier 12 isapplied to the windings 69 and 18 to release the brake l2.

Second forward position of controller Upon movement of controller 35from its first into its second forward, position segment 19 comes intoengagement with its respective stationary contact thus extending acontrol current circuit through lead 88, the previously closed contactsof lock-in relay 64 and lead 8| to the. winding of a second stepcontactor 82, the opposite terminal of which winding is joined by lead48 with supply main 23 This causes contactor 82 to close reducing theamount of resistance of grid 58 which is included in the secondarycircuit of motor II. Motor II is thus caused to rotate with increasedspeed. H

Closure of contactor 82 also brings about closure of auxiliary lock-incontacts 83 which prepares a circuit to be subsequently utilized.

Third forward position of controller Upon movement of controller 35 fromits second into its third forward position segment 84 is brought intoengagement with its respective stationary contact establishing a currentcontrol circuit'extending from lead 40 through lead 85, auxiliarylock-in contact 03 and lead 85 to one terminal of the winding of a thirdstep contactor 81. The opposite terminal of the winding of the thirdstep contactor 81 is joined by lead 88 with lead 48 thus completing acircuit which causes third step contactor 81 to close, thus furtherreducing the amount of resistance of grid 58 which is included in thesecondary circuit of motor II. At the same time auxiliary lock-incontacts 89 are caused to close thus preparing a circuit to besubsequently utilized.

Movement of the controller 35 into the third position also bringssegment 90 into engagement with its respective stationary contact thusextending a control circuit through lead 9| to one terminal of thewinding of a decelerating relay 52 the opposite terminal of whichwinding is joined by lead 93 with the lead 48. The relay 92 is thuscaused to close for the purpose of preparing certain circuits to besubsequently utilized. In closing, relay 02 establishes for itself amaintaining circuit extending from lead 40 through segment 56, itsrespective stationary contact, lead 94, and maintaining contacts 95 tolead 96. This maintaining circuit causes the relay 92 to remain closeduntil such time as segment 56 departs from its respective stationarycontact. This action of the relay 92 is preparatory, establishingconditions to be subsequently utilized in a manner later described.

Fourth forward position of the controller Upon movement of controller 35from its third into its fourth forward position, segment 91 is broughtinto engagement with its respective stationary contact thus extending acontrol current circuit from lead 40 through lead 58, auxiliary contacts80 and lead 09 to one terminal of the winding of a fourth step contactorI00. The opposite terminal of the winding of contactor I is joined by alead IDI with the lead 48 thus completing a control circuit which causescontactor I00 to close further reducing the amount of resistance of thegrid 58 which is included in the secondary circuit of motor II. Closureof contactor I00 causes closure of auxiliary lock-in contacts I02 forthe purpose of preparing a circuit to be subsequently utilized.

Fifth forward position of the controller Upon movement of controller 35from its fourth into its fifth forward position, segment I03 is broughtinto engagement with its respective stationary contact, establishing acontrol circuit extending from lead 40 through lead I04, lock-incontacts I02 and lead I05 to one terminal of the winding of a fifth stepcontactor I06. The opposite terminal of the winding of contactor I06 isjoined by a lead I 07 with lead 48 thus completing a control circuitwhich causes contactor I06 to close thus further reducing the amount ofrecaused to operate at its maximum speed.

Deceleration from the forward driving positions of the controller As thecontroller 35 is moved from the fifth to the fourth forward position thecontrol circuit of the fifth step contactor I06 is interrupted causingthe latter to open thus increasing the resistance in the secondarycircuit of motor II. Similarly when controller 35 is moved from thefourth to the third position the control current circuit of fourth stepcontactor I00 is interrupted causing the latter to open, furtherincreasing the secondary resistance of the motor II. Thus a driftingdeceleration of the bridge of the crane takes place upon shifting of thecontroller from its higher position.

In contrast movement of the controller 35 from the third to the secondforward position causes segment 68, previously mentioned to come intoengagement with its respective stationary contact thus establishing acontrol circuit extending from lead 50 through lead I08 to contacts I00of decelerating relay 92 which contacts are found in closed position byreason of an action previously described. The control circuit inquestion then extends through lead IIO to the winding of an excitationrelay II I and thence through lead I I2 to a connection with lead 48thus completing a control circuit which causes excitation relay III toclose.

The excitation current regulated by the relay I II is supplied by atransformer II3 the primary of which is connected through leads H4 andH5 with leads 40 and 4'! respectively. The secondary of transformer H3is connected by leads H6 and II! to the input terminals of a rectifierHi9. Rectified excitation current is drawn from the rectifier I59through the lead II8 which extends to the contacts of excitation relay III from whence it passes through lead I I9 resistance element I20resistance element IZI and sliding contact I22 into trolley conductorI23. Trolley conductor I23 is electrically joined in turn by lead I24with contacts I25 of power failure relay iZt. For reasons hereafterexplained the contacts I25 are in closed position if power supply isbeing maintained and for this reason the circuit in question continuesthrough lead I2? to the windings I 28 of the induced-current brake H.The excitation current circuit then extends from the windings I28through lead I29 to trolley conductor I30 and thence through slidingcontact I3i and lead I32 to the other output terminal of rectifier I49.Excitation current is thus supplied to the windings of eddy-currentbrake I'i in an amount determined by the resistance value of resistanceelements I28 and I2I.

Movement of the controller 35 from the third to the second position alsocauses segment 84 to become disengaged from its respective stationarycontact thus causing third step contactor 31 to open increasing furtherthe amount of resistance of grid 58 contained in the secondary circuitof motor II. With power supplied to motor I I thus further reduced inamount and with a resisting torque now being exerted by eddy-currentbrake I'I, excited as above explained, a smooth but positivedeceleration of the motor II and the crane driven thereby is broughtabout. As the rate of rotation of motor II decreases the resistingtorque of induced-current brake I! also decreases in well known mannerwhile at the same time,

since the use of brushes may be thus avoided and dependable operationsecured after long years of operation without attention. Thischaracteristic is important since normal operation of the apparatus willnot reveal a derangement of this particular part, which may be calledupon to act only infrequently and under conditions which are notexpected. Hereafter for convenience the term generator is therefore usedas meaning any suitable excitation source independent of the main powersupply.

A further advantage of bridge motion energized excitation of brake I1 isthat the apparatus stands ready to func ion whenever the crane is leftunattended with power supply interrupted. In such a case if there be aderangement of the brake l2, any force tending to put the bridge intomotion will be resisted so that the maximum speed which may be attainedwill be low enough so that stops at the ends of the runway will haltmovement of the bridge I without damage. Where cranes are installed inthe open, windstorms of unexpected severity sometimes occur andinstances of very extensive damage have arisen where cranes have beenput into motion by action of the wind at a time when the holding brake,such as brake I2, was not inproper functioning order. This hazard, asabove explained, is avoided in apparatuses constructed in accordancewith this invention by the self restraining action of the eddy-currentbrake i1, excited by current derived from alternator I53.

I claim:

1. In an electrically propelled apparatus having traction means, a drivesystem therefor comprising an electric motor; mechanical powertransmitting means drivingly connecting said motor to said tractionmeans; an induced current brake having a driven member connected to saidmotor in driven relationship thereto, a stationary member secured inbraking relationship to said driven member, and an excitation windingfor magnetizing said driving and driven members; an electric powersupply circuit connected to said motor including control means adaptedto be moved to and from an off position and an adjacent lower speed onzone and a more remote higher speed on zone, a preparatory deceleratingrelay comprising a winding for closing the same and lock-in contacts andbrake energizing contacts closeable when said winding is energized,preparatory contacts closeaole by said control means only on movement ofthe same into the higher speed on zone of the same in circuit with thewinding of said preparatory decelerating relay for actuating the same toclosed position, maintaining contacts closeable by said control meansthroughout the on zones thereof in circuit with the winding of saidpreparatory decelerating relay and the lockin contacts of the same formaintaining said relay upon closure in closed position until saidcontrol means is moved to oiT position, braking contacts closeable bysaid control means only in the lower speed on zone thereof in circuitwith the brake energizing contacts of said preparatory deceleratingrelay, and relay means having a winding connected in series with saidbraking contacts and said brake energizing contacts and having contactsin circuit with the excitation winding of said induced-current brake forsupplying excitation current thereto when said brakeing contacts andsaid brake energizing contacts both are closed.

2. In an electrically propelled apparatus having traction means, a drivesystem therefor comprising an electric motor; mechanical powertransmitting means drivingly connecting said motor to said tractionmeans; an induced-current brake having a driven member connected to saidmotor in driven relationship thereto, a stationary member secured inbraking relationship to said driven member, and an excitation windingfor magnetizing said driving and driven members; an electric powersupply circuit connected to said motor including control means adaptedto be moved to and from open and closed positions to apply and interruptthe supply of power to said motor; a normal excitation supply circuitconnected to the winding of said induced-current brake including controlmeans adapted to be shifted to excite and terminate excitation of saidbrake; interlockingmeans cooperatively associated with the power controlmeans for said motor and with the excitation current control means forsaid brake operative to cause said brake to be excited only on movementof said power control means for said motor from closed toward openposition; and an emergency excitation source for saidinduced-current'brake, an emergency excitation circuit joining saidsource and the winding of said brake, and means rendered operative uponfailure of the electric power supply for said motor for causing saidemergency excitation circuit to become closed.

3. The combination with an apparatus in accordance with claim 1 in whichthere is provided an electro-magnetically released normally set frictionholding brake mounted in braking relation to said motor, a normalholding brake circuit joining said holding brake to the electric powersupply for said motor operative to excite and release said brake whenpower is supplied to said motor, and in which the emergency excitationsource includes an emergency excitation source for said holding brakeand comprises a generator mechanically connected in driven relationshipwith said motor, a power failure relay means for said induced-currentbrake and said holding brake, an excitation circuit joining said holdingbrake and said induced-current brake to said generator through saidpower failure relay means, and an actuator circuit for said powerfailure relay means joining the same to the power supply for said motoroperative upon failure of said motor power supply to cause said powerfailure relay means to close said emergency excitation circuit tocontinue excitation of said induced-current brake and to retain saidholding brake in released position so long as the output of saidgenerator is sufficient.

4:. The combination with an apparatus in accordance with claim 2 inwhich there is provided an electro-1nagnetically released normally setfriction holding brake mounted in braking relation to said motor, anormal holding brake cir cuit joining said holding brake to the electricpower supply for said motor operative to excite and release said brakewhen power is supplied to motor, and in which the emergency excitationsource for said induced-current brake in cludes an emergency excitationsource for said holding brake and comprises a generator mechanicallyconnected in driven relationship with motor, a power failure relay meansfor said induced-current brake and said holding brake, an excitationcircuit joining said holding brake and said induced-current brake tosaid generator through said power failure relay means, and an actuatorcircuit for said power failure relay means joining the same to the powersupply for said motor operative upon failure-of said motor power supplyto cause said power failure relay means to close said emergencyexcitation circuit to continue excitation of said induced-current brakeand to retain said holding brake in released p sition so long as theoutput of said generator is sufficient, said power failure relay meansincluding contacts operative to open the normal excitation circuits ofsaid induced-current brake and said holdin brake upon closure of saidemergency excitation circuit.

5. The combination with an apparatus in accordance with claim 2 in whichthere is provided an electro-magnetically released normally set frictionholding brake mounted in braking relation to said motor, a normalholding brake circuit Joining said holding brake to the electric powersupply for said motor operative to excite and release said brake whenpower is supplied to said motor, and in which the emergency excitationsource for said induced-current brake includes an emergency excitationsource for said holding brake and comprises a generator mechanicallyconnected in driven relationship with said motor, a power failure relaymeans for said inducedcurrent brake and said holdingbrake, an excitationcircuit joining said holding brake and said induced-current brake tosaid generator through said power failure relay means, and an actuatorcircuit for said power failure relay means joining the same to the powersupply for said motor operative upon failure of said motor power supplyto cause said power failure relay means to close said emergencyexcitation circuit to continue excitation of said induced-current brakeand to retain said holding brake in released position so long as theoutput of said generator is sufilcient, said power failure relay meansincluding contacts operative to open the normal excitation circuits ofsaid induced-current brake and said holding brake in advance of closureof said emergency excitation circuit and transfer contacts operative toshunt said holding brake to delay release of the same durin the intervalbetween the opening of the normal excitation circuit for said holdingbrake and the closing of said emergency excitation circuit.

6. In a driving and braking circuit for electrically propelled apparatusthe combination comprising an electric propelling motor; an inducedcurrent brake having a driven member connected to said motor in drivenrelation thereto, a stationary member secured in braking relation tosaid driven member and an excitation winding for establishinga fieldmutual to said driving and driven members; an electric power supplycircuit including a controller for said motor, said controller having anoff position and positions for lower and higher speed driving of saidmotor; and an excitation current source for said excitation windingincluding switching means rendered active to complete a circuit betweensaid excitation current source and excitation winding when saidcontroller is in a lower speed position and said motor has been suppliedtheretofore with power to drive the same at a speed higher than saidlower speed.

7. In a driving and brakingcircuit for electrically propelled apparatusthe combination comprising an electric propelling motor; an inducedcurrent brake having a driven member connected to said motor in drivenrelation thereto, a stationary member secured in braking relation tosaid driven member and an excitation winding for establishing a fieldmutual to said driving and driven members; an electric power supplycircuit including a controller for said motor, said controller having anoff position and a plurality of driving positions for driving said motorat different speeds; and an excitation current source for saidexcitation windingincluding switching means rendered active to completea circuit between said excitation current source and said excitationwindin when said controller is placed in one of its said drivingpositions having been first moved from its said off position to apredetermined activating position.

8. In a driving and braking circuit for electrically propelled apparatusthe combination comprising an electric propelling motor; an inducedcurrent brake having a driven member connected to said motor in drivenrelation thereto, a stationary member secured in braking relation tosaid driven member and an excitation winding for establishing a fieldmutual to said driving and driven members; an electric power supplycircuit including a controller for said motor, said controller having anoff position and a plurality of driving positions for driving said motorat different speeds; and an excitation current source for saidexcitation winding including switching means rendered active to completethe circuit between said excitation current source and said excitationwinding when said controller is placed in a predetermined drivingposition after first being moved through a driving position more remotefrom said off position,

9. In a driving and braking circuit for electrically propelled apparatusthe combination comprising an electric propelling motor; an inducedcurrent brake having a driven member connected to said motor in drivenrelation thereto, a stationary member secured in braking relation tosaid driven member and an excitation winding for establishing a fieldmutual to said driving and driven members; an electric power supplycircuit including a controller for said motor, said controller having anoff position, a plurality of driving positions and a retarding position;and an excitation current source rendered active to complete a circuitbetween said excitation current source and said excitation winding whensaid controller has been moved first from its off position to one of itssaid driving positions and then to its said retarding position.

References Cited in the file of this patent UNITED STATES PATENTS

